Vibrational properties of delafossite CuGaO2 at ambient and high pressures -: art. no. 064301

In this paper we investigate the vibrational properties of CuGaO2 delafossite by means of Raman experiments and ab initio calculations. Both investigations have been performed at ambient pressure and also at high pressure. The two Raman-active modes have frequencies w(Eg)=368 +/- 1 cm(-1) and w(A1g)=729 +/- 1 cm(-1), and pressure coefficients 2.78 +/- 0.03 cm(-1)/GPa (E-g) and 4.64 +/- 0.09 cm(-1)/GPa (A(1g)). Raman experiments indicate the existence of a phase transition beginning at 26 +/- 1 GPa. At about the same pressure, ab initio calculations show the presence of a dynamical instability, possibly related to the phase transition. The phonon dispersion curves are also discussed.